1. Field of the Invention
The present invention relates generally to internal combustion engines and more particularly to a piston, having a novel ignition system embodied therein, for spark-igniting an air-fuel mixture within the internal combustion engine.
2. Description of the Background Art
Modem spark ignition engines are designed and constructed to maximize horsepower, torque, and fuel economy, and to at the same time reduce polluting exhaust emissions to a minimum. A lean air-fuel mixture (more air than fuel) is desirous in most cases because it yields increased fuel economy and lowered emissions, but at the cost of lowered horsepower and torque. Horsepower and torque are decreased because of the slow burn rate of the lean mixture. If the burn rate of the lean air-fuel mixture is increased, horsepower and torque are substantially increased as well.
High performance and racing engine applications would also benefit from increased burn rates. Because fuel economy is not a concern in high performance engines a richer air-fuel mixture is used to increase horsepower and torque. These engines, however, typically require high-octane fuels to compensate for higher compression ratios. Conversely, high-octane fuels burn slowly.
There have been two methods previously employed to improve the burn rate of an air-fuel mixture within the combustion chamber of spark-ignition engines. The first method is to add at most a second spark plug to each engine cylinder. Adding a second spark plug does not significantly increase the burn rate because each spark plug is seated in the same wall of the combustion chamber. Therefore, each spark plug produces a spark within close proximity of each other. Thus, the fire must still travel relatively long distances to ignite all of the air-fuel mix. The second method of increasing the burn rate of the air-fuel mixture is to increase the turbulence, or xe2x80x9cswirl,xe2x80x9d of the air and fuel entering the cylinder. This disperses the fuel more uniformly throughout the air and causes a more even, quicker burn. The burn rate of the fuel, however, is still relatively slow because the fire must propagate across the entire combustion chamber. In addition, the amount of swirl that can be introduced is limited because excessive turbulence produces a snuffing effect on the flame.
Most commonly, however, xe2x80x9cspark advancexe2x80x9d is used to compensate for slow burn times of high-octane and lean fuel mixtures. In particular, sparks are generated 32xe2x96xa1 to 38xe2x96xa1 of crankshaft rotation before the piston reaches top dead center on its compression stroke. This method is not ideal because energy is lost as the piston is compressing against the expansive force of the ignited air-fuel mixture. By increasing the burn rate of a rich, high-octane or lean air-fuel mixture, less spark advance is required. Thus, the piston would use less energy to compress the expansive, ignited air-fuel mixture, increasing both horsepower and torque.
What is needed is a system that increases the burn rate of an air-fuel mixture within a combustion chamber of an internal combustion engine. What is also needed is a system that generates multiple electrical arcs that are not within close proximity of each other for igniting the air-fuel mixture.
The present invention overcomes the problems associated with the prior art by providing a novel ignition system that increases the burn rate of a compressed air-fuel mixture within the combustion chamber of an internal combustion engine. A piston with an integrated electrode generates multiple electrical arcs to ignite the compressed air-fuel mixture at spaced apart locations in the combustion chamber.
In one embodiment of the present invention, an internal combustion engine includes at least one piston with an insulating guide formed in the piston for receiving an electrode. Spark to ignite the air-fuel mixture is generated by an electrode disposed within the insulating guide. A power plug disposed in a power plug opening transmits electrical power through the wall of the engine to the electrode.
The electrode, in one particular embodiment, comprises a body and at least one spark lead coupled to the body. When disposed within the insulating guide, a tip of the spark lead is positioned a predetermined distance (spark gap) from a point on the piston near the center of combustion chamber. The body is positioned with respect to the power plug such that providing electrical power to the power plug causes a first electrical arc between the power plug and the body and a second electrical arc between the tip of the spark lead and the piston at a predetermined time of engine operation. Thus, two simultaneous, spaced-apart sparks are provided to ignite the air-fuel mixture in the combustion chamber. Optionally, the piston further includes an arc insert disposed between the tip of the spark lead and the piston, to reduce ablation of the piston surface. The arc insert may comprise a piece of copper fixed to the piston.
In another particular embodiment of the invention, the electrode includes a body and a plurality of spark leads attached to the body. The insulating guide comprises a corresponding plurality of channels, each for receiving one of the plurality of spark leads. The insulating guides are shaped to position the tips of the spark leads within a predetermined distance (spark gap) from arc surfaces of the piston adjacent the end of each insulating guide. The insulating guides may be formed in a channel in the top surface of the piston from a ceramic material. The arc surfaces are spaced apart from one another to increase the burn rate of the air-fuel mixture.
Optionally, the electrode is removable, and can be inserted or removed through the power plug opening. For example, in one particular embodiment the spark leads of the electrode are flexible, and the insulating guide is tapered at a receiving end to facilitate easy insertion of the electrode in the insulating guide. The body of the electrode can be adapted to engage either the insulating guide or the conductive portion of the piston. For example, in one embodiment, the insulating guide includes a seat for receiving the body of the electrode. In this embodiment, the body of the electrode may be formed entirely of conductive material. Alternatively, if the body of the electrode is adapted to engage the piston, then the body includes an insulating portion for engaging the piston and a conductive portion for transmitting electrical power to the spark leads.